Boat trailers for transporting boats over land from one location to another behind a towing vehicle are well known in the art. Most commonly, such trailers are backed down a launching ramp into a body of water into which a boat is to be launched or from which a boat is to be pulled out of the water and onto the trailer by a manual or electrical winch. Once a boat has be launched from a trailer into a body of water, the trailer must be towed away and stored on land until needed again to remove the boat from the water. Frequently, a boat is launched once at the beginning of a boating season and remains in the water for the entire season before being pulled out of the water on the boat trailer to be stored on land in the off-season. As such, many boat trailers remain idle on land during the boating season where they take up space undesirably.
While many boats remain submerged to their waterlines in slips or at moorings for the duration of the boating season, it is common for boat owners to dock and store their boats on boat lifts which raise them above the water in order to maintain the cleanliness of their hulls and to prevent damage from waves. When it is desired to use the boat, it is lowered on the boat lift into the water to a point where it can float free of the boat lift. At the end of a boating season, the boat is pulled out of the water and stored on its trailer and the boat lift is removed from the water and stored on land as well.
Accordingly, one must typically incur the expense of owning both a boat trailer and a boat lift and have sufficient space to store both or else incur additional expense to rent storage space for one or both of the trailer and the lift. Added to the expense of owning and storing a trailer and a lift is the difficulty in removing the typical boat lift from the body of water, as well as positioning the boat lift at a suitable docking location. Often both operations require the cooperative efforts of several individuals. Furthermore, most boat lifts do not float, nor can they be maneuvered in a floatable manner in order to facilitate the process of positioning the boat lift in a suitable docking location.
At least one attempt at eliminating the difficulties identified above has been made and is the subject of U.S. Pat. No. 5,380,143 issued to Mohan on Jan. 10, 1995. Mohan discloses a lightweight combination boat trailer and lift which can transport a boat over land and elevate the boat above a body of water for docking and storage. Furthermore, the Mohan device is capable of being maneuvered about the body of water in a floatable manner to facilitate its being positioned in a suitable docking location for the duration of the boating season. However, while the Mohan device represents an improvement over the prior alternative of owning and storing a separate trailer and lift, each of the two preferred embodiments through which Mohan teaches his invention has particular limitations and disadvantages.
In a first preferred embodiment, Mohan teaches a lightweight combination boat trailer and lift including a lightweight support frame, at least three adjustable support legs adjustably secured to the support frame and a cable and winch assembly secured to the support frame and the support legs for elevating the support frame above the body of water. Among the disadvantages of this first embodiment are its very elaborate cable and winch system for simultaneously moving the adjustable support legs in the same direction and the fact that when the support frame and boat are elevated on the support legs, the center of mass of the trailer and boat is high above the floor of the body of water and there is nothing to stabilize the support legs such that their lower ends will not move with respect to one another to prevent bending or possible collapse thereof in high winds and/or turbulent water.
Although the second preferred embodiment of the Mohan device has a much simpler cable and winch system and appears to provide a much more stable footing on the floor of the body of water than the first embodiment, the second embodiment has at least one notable disadvantage of its own: the footing of the three adjustable support legs is not firmly fixed on the floor of the body of water. Specifically, on each occasion on which the boat is lowered or elevated, the entire combination boat trailer and lift of Mohan's second embodiment must move with respect to the floor of the body of water. It will be appreciated that the entire combination in this embodiment may "crawl" unpredictably along the floor of the body of water absent some external means of anchoring it in place.